8. a3 has the obvious response of Bxc3 (and it will be nearly impossible to get votes for anything else). However, at the very least for discussion purposes, Ba5 is interesting in that it leads the game in a profoundly different direction. Black may get the IQP, and essentially dumps the queen-side for a quick attack against the king. Here is an example (albeit a little dated)
As expected, Nc6 is winning in a land slide. Let's go over his possible resonses
8. a3
8. cxd5
8. dxc6
or any other novelty you are aware of.